Certain EPDM copolymer/maleic anhydride adducts and thermoplastic elastomers therefrom

ABSTRACT

An adduct of maleic anhydride and an elastomeric copolymer of ethylene, at least one C3-C6 Alpha -olefin, and at least one nonconjugated diene; the adduct having an inherent viscosity of at least one as measured on 0.1 gram of adduct dissolved in 100 milliliters of perchloroethylene at 30*C. and having a gel content less than about 5 percent as measured by weight percent adduct insoluble in boiling tetrahydrofuran at atmospheric pressure after 48 hours. Also, a process of making the adduct and thermoplastic elastomers prepared from the adduct.

United States Patent n 1 Caywood, Jr.

[4 1 May 20, 1975 CERTAIN EPDM COPOLYMER/MALEIC ANHYDRIDE ADDUCTS ANDTHERMOPLASTIC ELASTOMERS THEREFROM [75] Inventor: Stanley WilliamCaywood, Jr.,

Wilmington, Del.

[73] Assignee: E. l. du Pont de Nemours & Company, Wilmington, Del.

[22] Filed: Jan. 10, 1973 [21] Appl. No.: 322,360 I 52 us. Cl. 260/78.4D; 260/875 [51] Int. Cl C08f 15/40; C08f 27/04 [58] Field of Search260/78.4 D, 78.5 BB, 875

v [56] References Cited UNITED STATES PATENTS 2,608,550 8/1952Rowland... 260/785 2,844,502 7/1958 Paxton 161/92 2,933,480 4/1960Gresham et a1... 260/80.5

3,231,498 l/1966 de Vries 252/56 3,240,762 3/1966 Wilks et al 260/78.4

3,260,708 7/1966 Natta 260/795 3,403,011 9/1968 Sweeney 44/62 3,427,1832/1969 Portolani et al. 117/76 3,527,736 9/1970 Averink et a1. 260/7843,567,691 3/1971 Van Breen et al..... 260/784 D 3,644,248 2/1972 Luijket al 260/237 M Primary ExaminerJoseph L. Schofer AssistantExaminer-John Kight, lll

57 ABSTRACT An adduct of maleic anhydride and an elastomeric copolymerof ethylene, at least one C -C a-olefin, and

22 Claims, No Drawings CERTAIN EPDM COPOLYMER/MALEIC ANHYDRIDE ADDUCTSAND THERMOPLASTIC ELASTOMERS THEREFROM BACKGROUND OF THE INVENTION Thisinvention relates to adducts prepared by the thermal addition of maleicanhydride to elastomeric copolymers of ethylene and propylene which havea substantially saturated hydrocarbon backbone chain and unsaturatedhydrocarbon side-chains. This invention also relates to thermoplasticelastomers prepared from such adducts.

Grafting of maleic anhydride to polyolefins by free radical initiatedreactions is well known in the art. US. Pat. No. 3,236,917 to Natta etal, for example, discloses adducts prepared by heating a mixture ofethylene/propylene copolymer and maleic anhydride in the presence of anorganic peroxide which initiates the addition reaction by the generationof free radicals. Among other reactions, a molecule of maleic anhydridegrafts onto two copolymer chains thereby crosslinking the polymer. Thiscross-linking is irreversible. The adduct may be further cross-linked bya basic compound such as zinc oxide.

Numerous other suggestions have been made for grafting maleic anhydrideto synthetic elastomers, followed by cross-linking with a metal oxide toform a thermoplastic elastomer. US. Pat. No. 3,644,248 to Luijk, forexample, discloses addition of maleic anhydride to polyisoprene duringmastication or in the pres- -ence of an organic peroxide followed bycross-linking with a Group II or IV divalent'metal oxide.

Such processes utilize free radicals, either generated by shearingstresses during mastication or by heating organic compounds such asperoxides, to prepare the maleic anhydride/elastomer adduct. The freeradical mechanism of adduct formation, however, has certaindisadvantages. Namely, free radicals cause a molecule of maleicanhydride to add to two elastomer molecules,

thereby cross-linking the elastomer. Free radicals can also react withthe elastomer to introduce cross-linking. The degree of cross-linking inraw elastomeric polymers is commonly expressed in terms of gel content.

Uncontrolled cross-linking, as shown by a high gel content, tends tocause the uncured elastomeric polymer to have poor processingcharacteristics such as poor milling properties and slow extrusionrates. Poor tensile strengths and short break are also commonly observedin cured elastomers derived from elastomeric polymers which, in the rawor uncured state, have high .gel content.

The art has proposed use of free radical inhibitors to I SUMMARY OF THEINVENTION This invention provides adducts prepared by the thermaladdition of maleic anhydride to elastomeric copolymers of ethylene, atleast one C to C oz-olefin,

and at least one nonconjugated diene. The adducts have an inherentviscosity of at least one as measured on 0.1 gram of adduct dissolved inmilliliters of perchloroethylene at 30C. and have a gel content lessthan about 5 percent as measured byweight percent adduct insoluble inboiling tetrahydrofuran at atmospheric pressure after 48 hours.

The adducts are particularly suited for the prepara-' tion ofthermoplastic elastomers by curing the adduct with a metal salt of aweak acid, preferably in the presence of a promotor having an activehydrogen atom.

DETAILED DESCRIPTION OF THE INVENTION Elastomeric copolymers ofethylene, at least one C to C or-monoolefin, and at least onenonconjugated diene are well known in the art. These copolymers have asubstantially saturated hydrocarbon backbone chain which causes thecopolymer to be relatively inert to ozone attack and oxidativedegradation and have sidechain unsaturation available for sulfur curing.

These copolymers are conveniently prepared by copolymerizing themonomers in the presence of a coordination catalyst system such asdiisobutylaluminium chloride and vanadium oxytrichloride. Copolymerization may be conducted in an inert solvent or in a slurry or particleform reactor. Details of their preparation are given, for example, inUS. PatL'No. 2,933,480; 2,962,451; 3,000,866; 3,093,620; 3,093,621;3,063,973; 3,147,230; 3,154,528; 3,260,708; and in M. Sittig, StereoRubber and Other Elastomer Processes, Noyes Development Corporation,Park Ride, N.J., 1967.

Propylene is normally selected as the a-mon'o-olefin in preparing suchcopolymers because of its availability and for reasons of economics.Other lower a-monoolefins, such as l-butene, l-pentene, and l-hexene canbe selected in place of or in addition to propylene in preparingelastomeric copolymers which are useful in practicing the invention. Theterm EPDM as used herein refers to the preferred copolymers of ethylene,propylene, and at least one nonconjugated diene.

An especially preferred class of EPDM is that in which the nonconjugateddiene is monoreactive. Monoreactive nonconjugated dienes have one doublebond which readily enters the copolymerization reaction with ethyleneand propylene, and a second double bond which does not, to anyappreciable extent, enter the copolymerization reaction. Copolymers ofthis class have maximum side chain unsaturation for a given dienecontent, which unsaturation is available for adduct formation. Gelcontent of these copolymers is also minimal since there is minimalcross-linking during copolymerization.

Monoreactive nonconjugated dienes which can be selected in preparingthis preferred class of EPDM copolymer include linear aliphatic dienesof at least six carbon atoms which have one terminal double bond and oneinternal double bond, and cyclic dienes wherein one or both of thecarbon-to-carbon double bonds are part of a carbocyclic ring. Of thelinear dienes, copolymers of ethylene, propylene, and 1,4- hexadienehaving an inherent viscosity of at least about 1.5 are especiallypreferred.

Class of cyclic dienes useful in preparing the preferred class of EPDMcopolymers for adduct formation includes alkylidene bicycloalkenes,alkenyl bicycloalkenes, bicycloalkadienes, and alkenyl cycloalkenes.Representative of alkylidene bicycloalkenes are5-alkylidene-2-norbornenes such as 5-ethylidene-2- norbomene and5-methylene-2-norbornene. Representative of alkenyl bicycloalkenes are5-alkenyl-2- norbornenes such as 5-( l '-propenyl)-2-norbornene,5-(2-butenyl)-2-norbornene, and 5-hexenyl-2- norobornene.Dicyclopentadiene and 5-ethyl-2,5- norbornadiene are illustrative ofbicycloalkadienes, and vinyl cyclohexene is representative of alkenylcycloalkenes which may be selected as the diene monomer. EPDM copolymersprepared from cyclic dienes preferably have an inherent viscosity withinthe range of about 1.5 to 3.0, as measured on 0.1 gram copolymerdissolved in 100 milliliters ofperchloroethylene at 30 C., for optimumprocessing properties. Of the cyclic dienes, 5-ethylidene-2-norborneneis preferred.

Another class of preferred copolymers includes branched tetrapolymersmade from ethylene, at least one C to C a-monoolefin with propylenebeing preferred, at least one monoreactive nonconjugated diene, and atleast one direactive nonconjugated diene such as 2,5-norbornadiene or1,7-octadiene. By direactive is meant that both double bonds are capableof polymerizing during preparation of the copolymer. Tetrapolymers ofthis class preferably have an inherent viscosity of about 1.2 to 3.0, asmeasured on 0.1 gram copolymer dissolved in 100 milliliters ofperchloroethylene at 30C., for optimum processing properties. Apreferred copolymer of this class is a tetrapolymer of ethylene,propylene, 1,4-hexadiene, and 2,5-norbornadiene. Such copolymers aredescribed in Canadian Pat. Nos. 855,774 and 897,895. 1

Copolymers of the classes defined above have low gel content, asubstantially saturated hydrocarbon backbone which is resistant to ozoneand oxidative degradation, and hydrocarbon side-chain unsaturation whichpresents a situs for the thermal addition of maleic anhydride. Low gelcontent is indicative of a polymer having favorable processingproperties.

Using a copolymer of ethylene, propylene, and 1,4- hexadiene, thermaladdition of maleic anhydride to the copolymer is theorized to occur bythe following equation:

Polymer Backbone W (5H CH CH 4- Heat HC C C CH3 0 O O A molecule ofmaleic anhydride adds to the polymer at the site of side chainunsaturation to give a succinic anhydride radical bonded to the sidechain. Side chain unsaturation shifts by one carbon atom. It will beunderstood that side chain unsaturation can also shift away from thebackbone chain when the unsaturation is several carbon atoms removedfrom the terminal side chain carbon atom, as in copolymers of ethylene,propylene, and l,4-octadiene.

The adducts of this invention can be prepared by any process whichintimately mixes maleic anhydride with the copolymer without appreciablegeneration of free radicals, and which concurrently or subsequentlyheats the mixture to a temperature whereat thermal addition occurs.Selected temperatures will generally be at least 225C. to obtain adductformation at acceptable rates and less than about 350C. to avoid anysignificant polymer breakdown. Preferred temperature ranges will varywith the particular polymer and can readily be determined by one skilledin the art.

Mixing of the maleic anhydride and copolymer can be by blending moltenanhydride with copolymer in an internal mixer or extruder, or byblending finely divided dry maleic anhydride with copolymer on awellventilated rubber mill with concurrent or subsequent heating, suchas in a hot press or mold. Temperatures necessary to achieve thermalgrafting are sufficiently high to dehydrate maleic acid, forming maleicanhydride in situ. Thus, maleic acid can be compounded with thecopolymer instead of maleic anhydride when such is desired. The maleicanhydride can be substituted with groups, such as bromine or chlorine,which do not unduly interfere with the graft reaction.

Preferred copolymers of ethylene, propylene, and 1,4-hexadiene are veryresistant to free radical formation under high shear stress conditionsand are readily mixed on conventional bulk processing equipment withoutgel formation Care must be exercised, however, in selecting the mixingconditions for copolymers derived from strained ring dienes such asethylidene norbornene. Such copolymers will readily. generate freeradicals when sheared at low temperatures, and are preferably mixed withmaleic anhydride at high temperature, such as above C. to avoidappreciable gel formation. A

It is generally desired to form adducts containing about 0.5 to 9percent, and preferablyabout l to 4 percent, by weight maleic anhydride.Adducts containing such quantities of maleic anhydride have sufficientcarboxylated sites for ionic curing or grafting of the copolymer. Toachieve a desired degree of adduct formation within a reasonable time,high concentrations of reactants are helpful. One will generally selecta polymer having about twice the amount of side-chain unsaturation as isstoichiometrically required for the desired amount of maleic anhydrideincorporation. Similarly, about twice as much maleic anhydride is addedas is desired in the polymer adduct. Conversion of about 40 to 50percent of the maleic anhydride will result in co- Polymer Backbone WWHC ---CH C polymer adduct having the desired composition. For example,if one desires to obtain an ethylene/- propylene/1,4-hexadiene copolymerhaving 2.2 weight percent maleic anhydride content, he couldconveniently mix a copolymer having 0.49 moles side-chain unsaturationper kilogram of polymer with 0.49 moles maleic anhydride and heat themixture to convert 45 percent of the anhydride, thereby obtaining thedesired product.

Unreacted maleic anhydride is conveniently removed from the adduct byextraction with water. During washing, a portion of grafted maleicanhydride (now a succinic anhydride) is hydrolyzed to grafted succinicacid. When the polymer adduct is used to prepare a thermoplasticelastomer, it is not necessary to regenerate the anhydride groups.

If desired, the anhydride groups are readily regenerated by heatingwhile removing evolved water vapor. The heating can conveniently beaccomplished while subjecting the graft polymers to mechanical shearingwhich generates at least a portion of the required heat. For instance,the graft copolymer can be processed on a rubber mill at 120C. toregenerate anhydride groups. Alternatively, anhydride groups canconveniently be regenerated by heating sheets of the graft copolymerovernight at l C. in a vacuum oven. Higher heating temperatures expediteregeneration.

Unreacted maleic anhydride can also be removed from the copolymer/maleicanhydride adduct by dissolving the adduct in a solvent which will notdissolve maleic anhydride, such as hexane, decanting the solution, andrecovering the adduct from solution. Alternatively, both adduct andunreacted maleic anhydride are dissolved in a mutual solvent, such astetrahydrofuran. followed by precipitation of the adduct with anonsolvent such as anhydrous acetone. Unreacted maleic anhydride remainsin the acetone/tetrahydrofuran solutron.

The adducts of this invention have a substantially saturated hydrocarbonbackbone chain and have an inherent viscosity of at least 10, preferablyat least 1.5, as measured on 0.1 gram graft copolymer dissolved in 100milliliters of pcrchloroethylene at 30C. The adducts have a gel contentless than 5 percent, and generally less than 2 percent, as measured byweight percent adduct which is insoluble in boiling tetrahydrofuran atatmospheric pressure after 48 hours. Low gel content indicates that theadducts can readily be blended with agents such as carbon black,antioxidants, etc., using standard equipment such as a rubber mill orextruder.

The adducts have special utility in preparation of thermoplasticelastomers. In such applications the adduct is compounded with a metalsalt of a weak acid and then heated to form salt aggregates betweenadduct molecules.

Preferred metal salt curing agents are divalent Group II A or B metalsalts of weak acids. Included in this preferred group are metal oxides,such as magnesium or preferably Zinc oxide, and metal salts of weakcarboxylic acids, phenoxides, and ,B-diketonates such as calciumcatecholate and magnesium acetylacetonate. Metal salts of other groupsmay be selected. For example, the curing agent can be sodium acetate,potassium carbonate, copper acetylacetonate, tetraisobutyltitanate, tinoctoate, lead acetylacetonate, chromium acetylacetonate, nickelacetylacetonate, aluminum acetylacetonate or iron aetylacetonate.

The adduct curing rate will vary with the particular adduct, curingagent, curing temperature, intimacy of contact between adduct and curingagent, and whether the adduct cure sites are anhydride groups orcarboxylic acid groups formed by opening the anhydride groups. While thecuring agent will form salt aggregates with anhydride group cure sites,high temperatures such as 250C. are generally required to accomplishcuring within a reasonable time.

More favorable curing times and temperatures can be selected, andgenerally a better cure can be obtained, when the grafted anhydridegroups are open to and oleic acid) are also excellent accelerators sincethey produce water in situ during the neutralization as well as providesolubilization of the cation as discussed hereinafter. Amino acids (suchas 1 l-aminoundecanoic acid, 6-aminohexanoic acid, and.4-aminobutyricacid) are especially preferred as they convert small residual amounts ofunreacted maleic anhydride to innocuous form, removing the practicalrequirement that unreacted maleic anhydride be eliminated from theadduct prior to further processing. Other compounds useful asaccelerators include mercaptans, thiols, phenols, alcohols, and amines.

Polyfunctional accelerators, such as diamines. are generally avoidedwhen a thermoplastic product is desired since they may permanentlycross-link the adduct, forming an intractable product.

Accelerator may be introduced in a variety of ways. For instance, theadduct gradually absorbs sufficient water vapor to cause curing, in thepresenceof a curing agent, even at ambient temperatures. But thequantity of water absorbed is dependent on time and temperature, longtimes are required for favorable curingyand adduct compositions cured inthis manner do not possess predictable tensile properties.

More consistent and rapid curing is obtained by exposing compoundedadduct and curing agent to a controlled atmosphere of accelerator suchas steam or ammonia vapor. Alternatively, the compounded adduct can beimmersed in liquid accelerator such as aqueous potassium hydroxide orammonia. Preferably, liquid or solid accelerator is compounded with theadduct. Compounding is conveniently performed on a rubber mill or in aninternal mixer concurrent with the compounding of adduct and curingagent.

Selection of optimum quantities of curing agent is within the skill ofthe art. The optimum quantity will vary with the metal and counterion ofthe curing agent, and with the nature of the accelerator. Generally,percent neutralization is avoided when the only available anion for themetal is the grafted polymer carboxylate anion since intractable productmay be formed. By 100 percent neutralization is meant formation of saltaggregates at all available curing sites.

Most curing agents are not soluble in the adduct to any appreciableextent and only a small percent of the curing agent is actually involvedin curing. Unreacted curing agent generally does not greatly affect roomtemperature tensile properties of the cured adduct, and consequently,greater than stoichiometric quantities of curing agent are used. Moreefficient curing is obtained when a complexing ion is present whichsolubilizes the metal cation of the curing agent. For example, stearicacid may be used in conjuntion with zinc oxide to greatly reducethe-quantity of zinc oxide required to achieve desired tensileproperties. The stearic acid acts both as an accelerator and as asolubilizing agent for the zinc cation.

Especially favorable results-are obtained when compouns such as zincacetate dihydrate, hydrated zinc acetylacetone, and hydrated zinccatecholate are used alone as a curing agent or together with zinc oxideas an accelerator. such compounds provide water as an accelerator andalso help solubilize zinc oxide. When the counterion of zinc is notvolatile at curing temperatures, or when a nonvolatile anion such as theanion of stearic acid is also present, it has been found thatthermoplastic elastomeric adducts are prepared even at 100 percentneutralization.

Optimum curing conditions can readily be determined for a particularformulation of adduct, curing agent, and accelerator by testing tensileproperties obtained over a range of curing times and temperatures. Foradducts of maleic anhydride and ethylene/- propylene/1,4-hexadienecopolymer, excellent cures are obtained within 30 minutes at 160C. using4 phr. zinc acetate with a promoter, hydrated zinc catecholate alone orin combination with zinc oxide, or zinc oxide with 4-aminobutyric acidor 1 l-aminoundecanoic acid. When zinc oxide with stearic acid promoteris selected for curing, equivalent cures are obtained when the curingtime is extended at 160C. or when the curing temperature is raised to200C., although the cure is less reliable in that it depends somewhat onthe heat history of the adduct. l-lot mixing of the adduct and curingagents has been found to be especially beneficial in expediting curetimes.

Conventional additives such as carbon black and processing oils-may becompounded with the adduct prior to, concurrent, or subsequent to thecompounding with the divalent metal salt of a weak acid. Antioxidantsshould be added if the thermoplastic elastomer will be exposed toprolonged high temperature usage.

Adducts so cured possess tensile properties comparable to those achievedby conventional sulfur-curing techniques. They are thermoplasticmaterials and can readily be reshaped by heating to temperatures aboveabout 180C. Such thermoplastic elastomers can be processed in knownmanner, such as by extrusion or molding, to form films, hoses, and otheruseful articles of commerce such as gaskets.

The adducts 'may also be permanently cross-linked by polyfunctionalcuring agents, such as diamines, to prepare an elastomer which may beused in place of conventional sulfur cured EPDM rubbers. Thus, theirreversibly cured adduct may be used in the manufacture of hoses,gaskets, shock absorbers, and the like.

In addition, the uncured adduct has readily available carboxylated siteswhich can be used for grafting of functional groups to the elastomericcopolymer for special applications. For example, the uncured adduct canbe further reacted with pivalolactone to prepare thermoplasticelastomers as described in copending US. Pat. application Ser. No.268,056, filed June 30, 1972.

In the examples that follow all proportions, parts, and percentages areby weight unless otherwise indicated, and all testing is at C.inaccordance with ASTM standards unless otherwise indicated. Gel contentis that portion of the graft copolymer, in percent, which is insolublein boiling tetrahydrofuran at atmospheric pressusre after 48 hours.

Copolymer EPHD used in the examples has a Mooney (ML -1 4/12lC.)viscosity of about 35 and the following monomer unit composition:ethylene, 61.4 weight percent; propylene, 32 weight percent; 1,4-hexadiene, 6.6 weight percent. The copolymer has about 0.5 gram mole ofethylenic unsaturation per kilogram of copolymer. The Wallace plasticityis about 28 at 100C. The inherent viscosity, as measured on 0.1 gramcopolymer EPHD dissolved in 100 milliliters of perchloroethylene at30C., is about 2.0.

EXAMPLE 1 A Werner and Pfleider 53 mm twin screw extruder is assembledby end-to-end attachment of 16 barrel sections of /2 inch diameter.Following a short feed section are four reaction sections (zones 1-4),one vacuum port section (zone 5), a cooling section (zone 6), and

a die section. Provisions are made for the metering of molten maleicanhydride at the forward part of zone 1-. The screws are composed ofkneading blocks, reverse pitch screws, and transport screws arranged togenerate -200 psi pressure in, zones 1-4 and no pressure in zone 5. Thefree volume of zones l-5 is equivalent to two pounds of polymer atoperating temperature. Zones 1-4 are preheated to 300C, zone 5 to 260C.,and zone 6, the cross-head, and the die to 150C.

Copolymer EPHD is fed to the extruder in the form of chips which pass aA inch screen. Maleic anhydride is metered to the extruder at an averagefeed rate of 4.8 percent of the polymer weight. The screw speed is 12rpm and the vacuum port is operated at about 25 inches Hg.

The product, extruded at the rate of 6.15 lb/hr., has a maleic anhydridecontent of 2.23 percentas determined by a calibrated infrared method and2.19 percent by weight as determined by titration in tetrahydrofuranwith 0.1 M tetrabutylammonium hydroxide in methanol. Wallace plasticityof the product is 32 and gel content is lessthan about 5 percent.

Following purification of a small sample by solution in tetrahydrofuranand precipitation with anhydrous acetone, the maleic anhydride contentis 2.19 percent and 2.05 percent by weight, respectively, by infraredand titration determination. The gel content is less than about 5percent. The inherent viscosity is 1.5 as meaof perchloroethylene at30C.

EXAMPLE 2 A 4 inch X 8 inch rubber mill is used to mix'20 grams ofmaleic anhydride with 200 grams of copolymer EPHD at about 25C. Themilled mixture is then heated in a closed mold in a press at 260C. for30 minutes, and cooled to room temperature. The infrared spectrum of theproduct shows absorption bands characteristic of the anhydride group,and infrared quantitative analysis indicates a maleic anhydride contentof 2.4 percent by weight. Analysis for oxygen gives 1.3 percent byweight corresponding to 2.5 percent by weight maleic anhydride.

The reaction product is dissolved in hexane and filtered to remove asmall amount (about 5 percent) of insoluble polymer believed introducedin the copolymer feed. The hexane solution is washed with water toremove any free maleic anhydride and the polymer is precipitated byadding acetone to the hexane solution. The precipitated polymer contains2.1 percent by weight maleic anhydride by quantitative infrared analysisand 2.2 percent by weight maleic anhydride by oxygen analysis. The gelcontent is less than about 5 percent.

EXAMPLE 3 A 6 inch X 12 inch rubber mill is used to mix 50.

grams of maleic anhydride with 500 grams of copolymer EPHD. The mixtureis then heated in a closed mold in a press at about 288C. for 30minutes. The resulting adduct is washed with distilled water on a washmill to remove unreacted maleic anhydride and then heated in a vacuumoven at C. for 8 hours to dry the polymer and to convert grafted maleicacid (the anhydride being hydrolyzed by water washing) to grafted maleicanhydride. Infrared spectrum of the polymer shows only anhydrideabsorption. Quantitative infrared analysis shows the polymer contains3.7 percent by weight maleic anhydride. Gel content is less than aboutpercent.

EXAMPLE 4 To demonstrate prior art free radical grafting a mixture of100 grams of copolymer EPHD and 0.048 grams of Luperco 101 X Lcommercial organic peroxide and 5.88 grams of maleic anhydride isprepared on a well-ventilated rubber mill. The resulting mixture is thenheated in a closed mold for 45 minutes at 275C.

After heat treatment, the Wallace plasticity of the resulting adduct is95.5. The gel content, determined after the adduct has been treated byrefluxing tetrahydrofuran for 48 hours, is 70.5 percent. The solubleportion of the adduct contains 1.5 percent combined maleic anhydride byinfrared spectrum analysis. The insoluble portion is too highlycross-lined to be processed into a film for infrared analysis, andcannot be pro;

cessed on a rubber mill.

The procedure is repeated with the peroxide being increased to 0.386gram and the temperature reduced to 200C. The product is sufficientlycross-linked that a-film cannot be pressed. By blending the product withequal amounts of untreated polymer, a film can be" pressed and themaleic anhydride content of the product is determined to be 1.4 percent.This copolymer is too highly cross-linked to be compounded on a rubbermill.

EXAMPLE 5 insoluble material (3.5 wt. percent) is removed by fil- Adduct100 parts FEF Carbon Black 100 parts Naphthenic processing oil 50 parts1 l-Aminoundecanoic acid 4 parts Zinc Oxide 10 parts "'ASTM DesignationN-550 ASTM Designation D-2226 type I03 oil. Sayholt UniversalViscosities 87.2/2525 at 2lO"F/l00F.

A 3 inch X 6 inches sheet is cured in a closed mold for 30 minutes at160C. The cured product exhibits the following properties:

bromomaleic anhydride are compounded with 500 grams of copolymer EPHD.The compounded stock is heated for 30 minutes at 260C. in a 12 inch X 12inch x 0.5 inch mold, and then cooled. A IO-gram sample of the resultingadduct is dissolved by shaking for three days in hexane. Afterprecipitation by slow addition of tration through cheesecloth prior toisolation of the adduct. Precipitation, drying, and analysis as aboveshows incorporation of 1.1 weight percent anhydride for a 14 percentconversion. Ge] content is less than 5 percent.

B. Grafting with Dichloromaleic Anhydride Using the sme procedures as in(A), 500 grams of copolymer EPHD is compounded with 49.9 grams ofdichloromaleic anhydride. a sample is heated for 30 minutes at 260C. ina 12 inch X 12 inch X 0.075 inch mold and then cooled. Resulting adductreadily dissolves in tetrahydrofuran. The adduct is precipitated, dried,and scanned by IR, showing 2.9 weight percent anhydride for a 38 percentconversion. Gel content is less than 5 percent.

A second sample is heated for 30 minutes at 225C. in a 1 inch X 5 inch X0.075 inch mold, and then cooled. Resulting adduct can be pressed into afilm and it dissolves readily in hexane. Precipitation, drying, and

IR analysis shows 2.3 weight percent anhydride for a 29 7 percentconversion. A third sample, treated as above but using a 12 inch X 12inch X /2 inch mold contains 1.3 weight percent anhydride for a 17percent conversion. Gel content remains less than 5 percent.

EXAMPLE 7 copolymer used in this example has a Mooney viscosity (ML 14/121C.) of about 32 and the following monomer unit composition:ethylene, 50.6 percent; propylene, 45 percent;5-ethylidene-2-norbornene, 4.4 percent. It has an inherent viscosity of1.93 as measured on a solution of 0.1 gram copolymer in ml oftetrachloroethylene at 30C. This copolymer is identified as copolymerEPND..

Six grams of maleic anhydride are mixed with 100 grams copolymer EPND ofa cold, especially well ventilated 4 inch X 8 inch rubber mill operatedwith a sufficiently large nip to minimize shearing action. The mixtureis then heated in a press mold at 270 i 10C. for 45 minutes under apressure of 21 10 kg/cm gage. Unreacted maleic anhydride fumes escape onrelease of the pressure. Resulting adduct is cooled to room temperature.

Gel content of the adduct is less than about 5 percent. Five (5.0) gramsof the adduct are dissolved in tetrahydrofuran and precipitated by theaddition of acetone. The adduct is then dried for 24 hours under aslight nitrogen flow in a vacuum oven held at C. An infrared spectrum ofthe resulting film shows presence of anhydride moiety in an amount equalto 0.73 percent by weight maleic anhydride, for a conversion of 12percent.

The maleated EPND copolymer, an unmaleated EPND copolymer copolymer anda malleated EPHD copolymer (0.7 percent combined maleic anhydride)comparative sample are compounded on a rubber mill with the followingingredients:

100 parts Polymer FEF Black 100 parts Naphthcnic processing oil 50 parts1 l-Aminoundecanoic acid 4 parts Zinc oxide 10 pans '"As identified inExample 5 Slabs of the compounded polymer are cured in a press for 30minutes at 160C. Stress-strain properties are measured on an Instrontensile tester and results are recorded in Table I.

TABLE 1 12 Example 9 Adduct 100 parts FEF black 100 parts Naphthenic'petroleum oil 50 pans Stearic acid 2 parts Zinc oxide 10 parts "Asidentified in Example 5 Control EPND Copolymer Maleated Maleated(unmaleated) EPND Copolymer EPHD Copolymer M Kg/cm 13.0 19.0 34.1

Kg/em 13.0 28.5 66.8 M Kg/cm 38.0 86.1 T Kg/cm 12.7 43.9 89.8 E 245 425365 Permanent Set 49 29 8.5

at Break,

EXAMPLE 8 Physical properties are measured after heat treating the Anadduct of copolymer EPHD containing 3.7 percent combined maleicanhydride is compounded with FEF black (ASTM designation N-550) on a4inch X 8 inch rubber mill in the'proportion of 200 grams adduct to 100grams FEF black. Zinc oxide or magnesium oxide is milled into this stockas indicated in Table I1 and slabs 75 mils thick are pressed at 180C.for 30 minutes. Table I shows Instron stress-strain properties fordumbells subsequently cut from these slabs and pulled at C. and 100C.The 100C. test is performed on samples preheated 10 minutes at the testtemperature. Both magnesium oxide and zinc oxide stocks retain goodproperties at 100C.

compounded adduct in a press for various times at 160C. Results aregiven in Table 111.

' TABLE I11 TABLE 11' ZnO, 4 phr ZnO, 6 phr MgO, 2 phr MgO, 4 phr inn.Kg/Cl'fl 53 67 56 53 M Kg/cm 1 12 140 92 105 am. Kg/cm 169 197 134 144 TKg/cm" 176 204 144 151 n 340 335 455 350 Permanent Set 5 5 15 10 atBreak, 7c-

100C. test M Kg/cm 42 56 21 28 M Kg/cm" 49 74 21 28 M300, Kg/cm 56 r 81T Kg/cm 56 84 21 28 n 320 320 260 260 Permanent Set 39 74 58 at Break,

Compression set 22 hrs. at 70C. 92 87 98 100 Test at 25C.

Shore A hardness Test at 25C. 74 76 EXAMPLE 10 Sample A is prepared inthe same manner as shown in Example 9 except for the substitution ofzinc acetate dihydrate accelerator for stearic acid. Sample B has thesame formulation as Sample A but is prepared by mixing the curingingredients with a black-oil masterbatch for 10 minutes in a Brabenderinternal mixer at 160 to 190C. Data of Table IV demonstrates that hotmixing results in a composition which is more rapidly cured.

TABLE IV An adduct of copolymer EPHD containing 3.7 percent maleicanhydride is mill-mixed with 50 parts FEF black per 100 parts adduct.Slabs of resulting composition, 75 mils and 25 mils thick, are exposedto gaseous ammonia for minutes at room temperature. Properties of theblack loaded treated adduct are then measured and recorded in Table V.

For comparison copolymer EPHD is compounded on a rubber mill in astandard recipe of one part stearic acid, 5 parts zinc oxide, 80 partsFEF black, 40 parts paraffinic petroluem oil, 0.5 parttetramethylthiuran disulfide, 1.5 parts sulfur, 1 part2,2'-dithiobis(benzothiazole), and 2 parts zinc dibutyldithioc arbamateper 100 parts terpolymer. The compounds stockis cured minutes at 160C.and properties are measured and recorded in Table V.

14 TABLE V1 Masterbatch Mastcrbatch A B Control 5 Copolymer EPHD adductI00 Copolymer EPHD I00 FEF Black" 100 100 Naphthenic Oil" 50 50 Stearicacid 2 1 Zinc Oxide 5 5 Zinc dibutyldithiocarbamate 2 l0Tetramethylthiuram disulfidc 0.5

Z-Mercaptobenzothiazolc I Sulfur 15 Zinc acetylacetonate, hydrated 2. 8

Hardness, Shore A 73 69 m, g/ 65 79 15 200 g/cm 124 150 kg/cm I70 kg/cm186 163 1: 355 226 Permanent Set at Break, l5 2 '"As identified inExample 5 EXAMPLE 13 A. Tetrapolymer Copolymer used in this example is abranched tetrapolymer having a Mooney (ML l 4/12lC.) vis- 5 cosity of 20and the following monomer unit compositetrachloroethylene at 30C. Thereare about 0.54

gram-moles of ethylenic side-chain groups per kilogram of tetrapolymer.

B. Adduct of tetrapolymer and maleic anhydride A heavy-duty single screwtype extruder is used having a 1.5-inch l.D. barrel. The length isapportioned as follows: feed section, 10.5 inches; compression section,6.5 inches; injection section, 1.625 inches; mixing torpedo, 5.5 inches;and the second'mixing section, 8.5 inches. The extruder'is jacketed andheated by'oil cir- 40 culating at 308 to 318C. Temperature inside thebarrel is at least 260C. and the pressure is 28.1 to 35.2 kg/cm Thescrew turns at 15 rpm.

TABLE V Ammonia Treated Ammonia Treated Sulfur cured -mil slab of 25-milslab of Copolymer EPHD* adduct adduct M kg/cm 46 63 M kg/cm 83 91 I20 Mkg/cm" 134 170 T ,kg/cm 151 141 176 H 370 330 330 Permanent Set 8 8 atBreak Control Exampale 12 Copolymer of Part A is added to the feedhopper at a rate of 2.74 kg/hr.; maleic anhydride is injected at thebeginning of the mixing section at the rate of 0.17 kg/hr. Resultingadduct leaves the extruder and is 60 passed directly into water wherecooling and extraction of some of the unreacted maleic anhydride occur.Adduct is then freed from water and additional unreacted maleicanhydride in a vacuum oven at C. Gel content of the adduct is less than5 percent.

C. Thermoplastic Elastomer Adduct of Part B is compounded on a rubberroll mill according to the following recipes:

Component Sample A Sample B Adduct 100 I 4,4'-Thio-bis(6-tert.- 0. 0.5

hutylrm-cresol) FEF carbon black l0() 0 Naphthenic petroleum 75 6O 0W2!Hard kaolin clay 0 l0() TiO 0 20 H N(CH CO H 3 3 ZnO 2.7 2.7

ASTM Designation N550 Y "'ASTM D 2226 type 103 oil. Sayholt Universal!Viscositics 872/2525 at Z l ()"l l 00F.

"Equivalent analysis: 44-4671 silica, 37.5-39.571 alumina. [.5-27: ironoxide. and l-2% titanium dioxide. ignition loss 13.9-14.271. Specificgravity of 2.60. pH in water 4.5-5.5, 325 mesh residue of 0.17%.

*Ti-Purc" 902 by Du Pont.

Compounding of adduct with antioxidant and carbon black or clay (SamplesA and B respectively) is at about 100C. Thereafter the temperature islowered to about 50C. and the remaining components are incorporated,with zinc oxide being incorporated last. The resulting compositions areheated at 100C. for one hourin an oven to form the correspondingthermoplastic elastomers which are then cooled and chopped into smallpellets.

D. Extrusion of Thermoplastic Elastomers Pellets of black loadedelastomers (Sample A of Part C) are added to the feed hopper of aninjection molding machine having barrel and nozzle temperatures about250C., booster injection pressure of 70.3 kg/cm fast ram speed and 96rpm screw speed. A 20- sec./20-sec. filling/cooling cycle is employed.The mold temperature is l 14C. Typical extrudates are shiny ans smoothwith excellent die definition. Shrinkage is 7.5

percent. j j

Pellets of clay loaded elastomer (Sample B of Part C) are injectionmolded using the same machine but with a barrel and nozzle temperatureabout 225C; booster injection pressure of 57.6 kglcm and moldtemperature of 80C. Ram speed, screw speed, and filling/cooling cycle isthe same. Smooth extrusion occurs; shrinkage is 8 percent. When hot, theclay loaded compounds are quite tacky. Their surfaces are somewhatmatted by demoldin g.

EXAMPLE 14 This example demonstrates remolding of the thermoplasticelastomer.

The following ingredients are mixed for minutes '"Containing 2.271grafted maleic anhydride "Same as in Example l3 Thermoplastic elastomerthus obtained is pressed into a sheet at 200C. and then compressionmolded into a 3 inch X 6 inch X 0.075 inch slab and into Yerzley pelletsat 200C. for 10 minutes. Physical properties are tested and recorded inTable VII for this first molding. After physical testing, the remainsare pressed into a 1 inch X 5 inch X 0.075 inch slab at 200C. for 10Molded Once Twice Thrice M kg/cm 88.6 98.4 96.0 M,,,,. kg/cm 168 177 I82T kg/cm 202 197 199 E 72 290 245 255 Shore A hardness 7l 7| 7! What isclaimed is: 1. An adduct of maleic anhydride and an elastomericcopolymer of ethylene, at least one C to C a-olefin,

and at least one nonconjugated diene; the adduct having an inherentviscosity of at least one as measured on 0.1 gram of adduct dissolved inmilliliters of perchloroethylene at 30C. and having a gel content lessthan about 5 percent as measured by weight percent adduct insoluble inboiling. tetrahydrofuran at atmospheric pressure after 48 hours. 8

2. The adduct of claim 1 wherein the'elastomeric-copolymer is acopolymer of ethylene, propylene, and at least one of a linear aliphaticdiene of at least six carbon atoms having one terminal double bond, anda cyclic diene with at least one double bond in a cyclic ring.

3 The adduct of claim 1 wherein the elastomeric copolymer is a copolymerof ethylene, propylene, and l,4-hexadiene having an inherent viscosityof at least about 1.5, and the adduct contains about 0.5 to 9 percent byweight maleic anhydride.

4. The adduct of claim 3 wherein the adduct contains about l to 4percent by weight maleic anhydride and has a gel content less than about2 percent.

5. The adduct of claim 1 wherein the elastomeric copolymer is acopolymer of ethylene, propylene, and at least one of an alkylidenebicycloalkene, alkenyl bicycloalkene, bicycloalkadiene, and an alkenylcycloalkene.

6. The adduct of claim 5 wherein the nonconjugated diene is5-ethylidene-2-norbornene, the elastomeric copolymer has an inherentviscosity of about 1.5 to 3.0, andthe adduct contains about 0.5 to 9percent by weight maleic anhydride.

7. The adduct of claim 1 wherein the elastomeric copolymer is acopolymer of ethylene, propylene, a monoreactive nonconjugated diene,and at leastone direactive nonconjugated diene.

8. The adduct of claim 7 wherein the elastomeric copolymer is atetrapolymer of ethylene, propylene, 1,4- hexadiene, and2,5-norbornadiene having an inherent viscosity of about 1.2 to 3.0; andthe adduct contains about 0.5 to 9 percent by weight maleic anhydride.

9. A thermoplastic elastomer obtained by curing 1. an adductof maleicanhydride and an elastomeric copolymer of ethylene, at least oneC; to Ca-olefin, and at least one nonconjugated diene; the adduct having aninherent viscosity of at least one'as 3. an accelerator having an activehydrogen atom.

10. The thermoplastic elastomer of claim 9 wherein the adduct is anethylene/propylene/nonconjugated diene copolymer containing about 0.5 to9 percent by weight maleic anhydride and the accelerator is at least oneof water, mercaptans, thiols, phenols, organic acids, alcohols, andamines.

11. The thermoplastic elastomer of claim whwerein the copolymer is anethylene/propylene.5- ethylidene-2-norbornene terpolymer.

12. The thermoplastic elastomer of claim 10 wherein the copolymer is anaethylene/propylene/l ,4- hexadiene/2,5-norbornadiene tetrapolymer.

13. The thermoplastic elastomer of claim 10 wherein the copolymer is anethylene/propylene/l,4-hexadiene terpolymer.

14. The thermoplastic elastomer of claim 9 wherein the copolymer is anethylene/propylene/ 1,4-hexadiene terpolymer having an inherentviscosity of at least 1.5, and said adduct contains about 1 to 4 percentby weight maleic anhydride.

15. The thermoplastic elastomer of claim 14 wherein said accelerator isat least one of zinc acetate dihydrate, hydrated zinc acetylacetone, andhydrated zinc catecholate.

16. The thermoplastic elastomer of claim 14 wherein zinc oxide is alsopresent.

17. The method of preparing an elastomeric adduct containing maleicanhydride, the adduct having a gel content less than about 5 percent asmeasured by weight percent adduct insoluble in boiling tetrahydrofuranat atmospheric pressure after 48 hours consisting essentially of l.mixing A. an elastomeric copolymer of ethylene, at least one C to Ca-olefin, and at least one nonconjugated diene, the copolymer having aninherent viscosity of. at least one as measured on 0.1 gram copolymerdissolved in 100 milliliters of perchloroethylene at 30C., and

B. maleic anhydride, and d 2. heating the mixture to a temperature ofabout 225 to 350C. 18. The method of claim 17 wherein the copolymer is acopolymer of ethylene, propylene, and at least one of a linear aliphaticdiene of at least six carbon atoms having one terminal double bond, anda cyclic diene with at least one double bond in a cyclic ring.

19. The method of claim 17 wherein the copolymer is anethylene/propylene/l,4-hexadiene terpolymer having an inherent viscosityof at least 1.5.

20. The method of claim 17 wherein the copolymer is anethylene/propylene/ l ,4-hexadiene/2,5- norbornadiene tetrapolymerhaving an inherent viscosity of about 1.2 to 3.0.

21. The method of claim 17 wherein the copolymer is anethylene/propylene/S-ethylidene-2-norbornene terpolymer having aninherent viscosity of 1.5 to 3.0.

22. A method of preparing a thermoplastic elastomer, said methodcomprising the following steps:

l. mixing A. an adduct of maleic anhydride with an ethylene-/propylene/l,4-hexadiene terpolymer, the proportion of maleic anhydridebeing about 7 l-4 weight percent of the adduct; the gel content of theadduct being less than about 2 weight percent as measured by theproportion of adduct insoluble in boiling tetrahydrofuran at atmosphericpressure for 48 hours; and the inherent viscosity of the adduct being atleast 1 as measured on 0.1 gram of adduct dissolved in ml. ofperchloroethylene at 30C.; and

B. an amount of at least one zinc salt selected from the groupconsisting of zinc acetate dihydrate,

hydrated zinc acetylacetone, and hydrated zinc catecholate effective tocure the adduct;

2. exposing the resulting mixture to at least one accelerator selectedfrom the group consisting of wa ter, mercaptans, phenols, organic acids,alcohols, and amines; and

3. heating the exposed mixture for a sufficien't time to cure theadduct.

1. MIXING A. AN ADDUCT OF MALEIC ANHYDRIDE WITH ANETHYLENE/PROPYLENE/1,4-HEXADIENE TERPOLYMER, THE PROPORTION OF MALEICANHYDRIDE BEING ABOUT 1-4 WEIGHT PERCENT OF THE ADDUCT; THE GEL CONTENTOF THE ADDUCT BEING LESS THAN ABOUT 2 WEIGHT PERCENT AS MEASURED BY THEPROPORTION OF ADDUCT INSOLUBLE IN BOILING TETRAHYDROFURAN AT ATMOLSPERIC PRESSURE FOR 48 HOURS; AND THE INHERENT VISCOSITY OF THE ADDUCTBEING AT LEAST 1 AS MEASURED ON 0.1 GRAM OF ADDUCT DISSOLVED IN 100 ML.OF PERCHLOROETHYLENE AT 30*C.; AND B. AN AMOUNT OF AT LEAST ONE ZINCSALT SELECTED FROM THE GROUP CONSISTING OF ZINC ACETATE DIHYDRATE,HYDRATED ZINC ACETYLACETONE, AND HYDRATED ZINC CATECHOLATE EFFECTIVE TOCURE THE ADDUCT;
 1. AN ADDUCT OF MALEIC ANHYDRIDE AND AN ELASTOMERICCOPOLYMER OF ETHYLENE, AT LEAST ONE C3 TO C6 A-OLEFIN, AND AT LEAST ONENONCONJUGATED DIENE; THE ADDUCT HAVING AN INHERENT VISCOSITY OF AT LEASTONE AS MEASURED ON 0.1 GRAM OF ADDUCT DISSOLVED IN 100 MILLITERS OFPERCHLOROETHYLENE AT 30*C. AND HAVING A GEL CONTENT LESS THAN ABOUT 5PERCENT AS MEASURED BY WEIGHT PERCENT ADDUCT INSOLUBLE IN BOILINGTETRAHYDROFURAN AT ATMOSPHERIC PRESSURE AFTER 48 HOURS.
 2. heating themixture to a temperature of about 225* to 350*C.
 2. EXPOSING THERESULTING MIXTURE TO AT LEAST ONE ACCELERATOR SELECTED FROM THE GROUPCONSISTING OF WATER, MERCAPTANS, PHENOLS, ORGANIC ACIDS, ALCOHOLS, ANDAMINES; AND
 2. exposing the resulting mixture to at least oneaccelerator selected from the group consisting of water, mercaptans,phenols, organic acids, alcohols, and amines; and
 2. The adduct of claim1 wherein the elastomeric copolymer is a copolymer of ethylene,propylene, and at least one of a linear aliphatic diene of at least sixcarbon atoms having one terminal double bond, and a cyclic diene with atleast one double bond in a cyclic ring.
 2. a Group II divalent metalsalt of a weak acid, and
 3. an accelerator having an active hydrogenatom.
 3. The adduct of claim 1 wherein the elastomeric copolymer is acopolymer of ethylene, propylene, and 1,4-hexadiene having an inherentviscosity of at least about 1.5, and the adduct contains about 0.5 to 9percent by weight maleic anhydride.
 3. heating the exposed mixture for asufficient time to cure the adduct.
 3. HEATING THE EXPOSED MIXTURE FOR ASUFFICIENT TIME TO CURE THE ADDUCT.
 4. The adduct of claim 3 wherein theadduct contains about 1 to 4 percent by weight maleic anhydride and hasa gel content less than about 2 percent.
 5. The adduct of claim 1wherein the elastomeric copolymer is a copolymer of ethylene, propylene,and at least one of an alkylidene bicycloalkene, alkenyl bicycloalkene,bicycloalkadiene, and an alkenyl cycloalkene.
 6. The adduct of claim 5wherein the nonconjugated diene is 5-ethylidene-2-norbornene, theelastomeric copolymer has an inherent viscosity of about 1.5 to 3.0, andthe adduct contains about 0.5 to 9 percent by weight maleic anhydride.7. The adduct of claim 1 wherein the elastomeric copolymer is acopolymer of ethylene, propylene, a monoreactive nonconjugated diene,and at least one direactive nonconjugated diene.
 8. The adduct of claim7 wherein the elastomeric copolymer is a tetrapolymer of ethylene,propylene, 1,4-hexadiene, and 2,5-norbornadiene having an inherentviscosity of about 1.2 to 3.0; and the adduct contains about 0.5 to 9percent by weight maleic anhydride.
 9. A thermoplastic elastomerobtained by curing
 10. The thermoplastic elastomer of claim 9 whereinthe adduct is an ethylene/propylene/nonconjugated diene copolymercontaining about 0.5 to 9 percent by weight maleic anhydride and theaccelerator is at least one of water, mercaptans, thiols, phenols,organic acids, alcohols, and amines.
 11. The thermoplastic elastomer ofclaim 10 whwerein the copolymer is anethylene/propylene,5-ethylidene-2-norbornene terpolymer.
 12. Thethermoplastic elastomer of claim 10 wherein the copolymer is anaethylene/propylene/1,4-hexadiene/2,5-norbornadiene tetrapolymer.
 13. Thethermoplastic elastomer of claim 10 wherein the copolymer is anethylene/propylene/1,4-hexadiene terpolymer.
 14. The thermoplasticelastomer of claim 9 wherein the copolymer is anethylene/propylene/1,4-hexadiene terpolymer having an inherent viscosityof at least 1.5, and said adduct contains about 1 to 4 percent by weightmaleic anhydride.
 15. The thermoplastic elastomer of claim 14 whereinsaid accelerator is at least one of zinc acetate dihydrate, hydratedzinc acetylacetone, and hydrated zinc catecholate.
 16. The thermoplasticelastomer of claim 14 wherein zinc oxide is also present.
 17. The methodof preparing an elastomeric adduct containing maleic anhydride, theadduct having a gel content less than about 5 percent as measured byweight percent adduct insoluble in boiling tetrahydrofuran atatmospheric pressure after 48 hours consisting essentially of
 18. Themethod of claim 17 wherein the copolymer is a copolymer of ethylene,propylene, and at least one of a linear aliphatic diene of at least sixcarbon atoms having one terminal double bond, and a cyclic diene with atleast one double bond in a cyclic ring.
 19. The method of claim 17wherein the copolymer is an ethylene/propylene/1,4-hexadiene terpolymerhaving an inherent viscosity of at least 1.5.
 20. The method of claim 17wherein the copolymer is anethylene/propylene/1,4-hexadiene/2,5-norbornadiene tetrapolymer havingan inherent viscosity of about 1.2 to 3.0.
 21. The method of claim 17wherein the copolymer is an ethylene/propylene/5-ethylidene-2-norborneneterpolymer having an inherent viscosity of 1.5 to 3.0.
 22. A METHOD OFPREPARING A THERMOPLASTIC ELASTOMER, SAID METHOD COMPRISING THEFOLLOEING STEPS: